10 Things You Might Not Know About the Elbow


The human body is an amazing thing. For each one of us, it's the most intimate object we know. And yet most of us don't know enough about it: its features, functions, quirks, and mysteries. Our series The Body explores human anatomy, part by part. Think of it as a mini digital encyclopedia with a dose of wow.

Unless you bang your funny bone or regularly play tennis, it's unlikely you spend a lot of time thinking about your elbow. But without this crucial joint, many daily activities would be impossible, explains Anand Murthi, attending orthopedic surgeon and chief of shoulder and elbow surgery at MedStar Union Memorial Hospital, in Baltimore, Maryland.


The elbow may seem small, but it requires three bones to make its simple hinging action possible. The humerus is a long bone that runs from the shoulder socket to the radius and ulna. (And yes, there's a school of thought that believes your "funny bone"—actually your ulnar nerve—is named as a play on the word humorous.) The radius is one of the two forearm bones, running down from the elbow to the thumb side of the wrist. Lastly, the ulna stretches away from the pinkie side of the wrist. Thanks to those three bones, your arm can hinge—making it possible to do a bicep curl, lift a bag, or rotate your hand.


The bones of the elbow are connected by numerous tendons and ligaments, including the ulnar collateral ligament, a fibrous tissue that connects the humerus to the forearm bones. This tendon is both important and vulnerable. When it ruptures or tears, you feel severe pain and can sometimes even see bruising on the inside of your arm. It's a surprisingly common sports injury, plaguing players of baseball, football, ice hockey, and golf. The other major ligament in the joint is called the radial collateral ligament. Located on the outside of the elbow, it prevents excessive extension of the elbow, and is less prone to injury.


At the lower end of the humerus are two rounded protrusions called epicondyles, which flare out from the bone. This is where muscles attach. The upper end of the ulna also has two protrusions, called the olecranon—which forms the pointy part of the elbow—and the caronoid process, a projection from the front of the ulna. Bone fractures, especially in children, often occur at these epicondyles, and are the most common short-term injuries of the elbow. Certain kinds of arthritis, especially in older patients with osteoarthritis, can also cause such severe degeneration here that an elbow replacement is necessary. (Since bones become more brittle as we age, it's wise to take steps to prevent falling or stumbling, as elbows are among the most likely casualties.)


Children love the thrill of a jump on the trampoline, but Barbara Bergin, an orthopedic surgeon in Austin, Texas, tells Mental Floss that she sees numerous fractures around the elbow in kids from doing just that. It's so common to break elbows and wrists this way, the American Board of Pediatrics warns against trampolines.


But the major muscles involved in bending your arm are the triceps—on the back of your arm—and biceps, on the front of your arm. Your many smaller flexor and extensor muscles allow you to move your wrists and fingers and rotate your forearm.


One of the most common conditions of the elbow is called "tennis elbow"—or lateral epicondylitis. Tennis players are prone to it, but it can be caused by any repetitive bending and flexing of the elbow, says Bergin. It's a painful degeneration of the tendons that attach to the bone on the outside of the elbow. It's so common, she says, "I probably see tennis elbow every day in my office." If the condition should strike you, Bergin says, "It's critical to stop doing whatever hurts. It will not get better if you continue to participate in whatever activity is causing pain." Full and total healing is required before you can return to the activities that gave you the condition in the first place.


When major league pitcher Tommy John injured his ulnar collateral ligament in 1974, his doctor opted to try a unique surgery to replace the deteriorated ligament with a tendon from somewhere else. Though the surgery can require a full year's recovery time—in Tommy John's case, it was nearly two and a half years and two surgeries—it's since become a time-tested method to repair this damaged ligament. Murthi tells Mental Floss, "New research on repairing the medial collateral ligament (versus reconstructing it) may lead to earlier recovery for Tommy John surgery. Also new treatments for articular cartilage damage, ligament reconstruction, and joint sparing techniques are evolving."


The elbow's close proximity to important blood vessels and nerves in your hand and arm make it a challenge to perform surgery on, Murthi says: "Careful, precise surgery is required to provide a good outcome. Often, rehabilitation with a skilled therapist is crucial to a good recovery." Currently, many operations are performed arthroscopically, so that surgeons can see all the various components as they make delicate maneuvers.


Should you have the misfortune of losing part of an arm, it's better to lose the parts below the elbow, Bergin says. This helps you maintain a range of motion and allows you to better manipulate a prosthesis. Fortunately, upper extremity amputations are rare and almost always result from accidents, as compared to lower arm amputations, which are often caused by some form of vascular disease.


While you may be tempted to read that latest hefty bestseller late into the night, if you're keeping your elbows bent in a sitting position for too long, you can get a case of ulnar neuritis, inflammation of the ulnar nerve—which can lead to numbness or weakness of the fingers and hand. Bergin warns, "It's much more common now than it used to be because we sit around for hours at a time on our phones." If you experience a "little tingly feeling in the pinky and fourth finger," she says, you've probably got a case. Her recommendation is to take as many breaks with your arms straight out as you can. Switch to a kindle or laptop that you can prop up to read at night. Be conscious of your ergonomics when you drive, type, and use your electronics.

‘Water’ in Kansas City Woman’s Ear Turned Out to Be a Venomous Brown Recluse Spider

N-sky/iStock via Getty Images
N-sky/iStock via Getty Images

Susie Torres, a resident of Kansas City, Missouri, woke up on Tuesday morning with the distinct feeling that water was lodged in her left ear. She likened it to the swooshing sensation that can often happen after swimming, WDAF-TV reports.

Instead of waiting for the problem to resolve itself, Torres went to the doctor—a decision that might have saved her from some serious pain. The medical assistant was the first to realize something was alarmingly amiss, and immediately called for backup.

“She ran out and said ‘I’m going to get a couple more people,’” Torres told 41 Action News. “She then said, ‘I think you have an insect in there.’” For many people, the thought of having any live insect stuck in an ear would be enough to cue a small- or large-scale freak-out, but Torres stayed calm.

The doctors “had a few tools and worked their magic and got it out,” Torres said. The “it” in question turned out to be a spider—and not just any harmless house spider (which you shouldn’t kill, by the way). It was a venomous brown recluse spider.

“Gross,” Torres told WDAF-TV. “Why, where, what, and how.”

Miraculously, the spider didn’t bite Torres. If it had, she would’ve ended up visiting the doctor with more than general ear discomfort: Brown recluse bites can cause pain, burning, fever, nausea, and purple or blue discoloration of the surrounding skin, according to Healthline.

Torres may have remained admirably level-headed throughout the ordeal, but that doesn’t mean she’s taking it lightly. “I went and put some cotton balls in my ears last night,” she told WDAF-TV. “I’m shaking off my clothes, and I don’t put my purse on the floor. I’m a little more cautious.”

Is this the first time an insect has posted up in the ear of an unsuspecting, innocent human? Absolutely not—here are six more horror stories, featuring a cockroach, a bed bug, and more.

[h/t WDAF-TV]

12 Fantastic Facts About the Immune System

monkeybusinessimages/iStock via Getty Images
monkeybusinessimages/iStock via Getty Images

If it weren't for our immune system, none of us would live very long. Not only does the immune system protect us from external pathogens like viruses, bacteria, and parasites, but it also battles cells that have mutated due to illnesses, like cancer, within the body. Here are 12 fascinating facts about the immune system.

1. The immune system saves lives.

The immune system is a complex network of tissues and organs that spreads throughout the entire body. In a nutshell, it works like this: A series of "sensors" within the system detects an intruding pathogen, like bacteria or a virus. Then the sensors signal other parts of the system to kill the pathogen and eliminate the infection.

"The immune system is being bombarded by all sorts of microbes all the time," Russell Vance, professor of immunology at University of California, Berkeley and an investigator for the Howard Hughes Medical Institute, tells Mental Floss. "Yet, even though we're not aware of it, it's saving our lives every day, and doing a remarkably good job of it."

2. Before scientists understood the immune system, illness was chalked up to unbalanced humors.

Long before physicians realized how invisible pathogens interacted with the body's system for fighting them off, doctors diagnosed all ills of the body and the mind according to the balance of "four humors": melancholic, phlegmatic, choleric, or sanguine. These criteria, devised by the Greek philosopher Hippocrates, were divided between the four elements, which were linked to bodily fluids (a.k.a. humors): earth (black bile), air (blood), water (phlegm) and fire (yellow bile), which also carried properties of cold, hot, moist, or dry. Through a combination of guesswork and observation, physicians would diagnose patients' humors and prescribe treatment that most likely did little to support the immune system's ability to resist infection.

3. Two men who unraveled the immune system's functions were bitter rivals.

Two scientists who discovered key functions of the immune system, Louis Pasteur and Robert Koch, should have been able to see their work as complementary, but they wound up rivals. Pasteur, a French microbiologist, was famous for his experiments demonstrating the mechanism of vaccines using weakened versions of the microbes. Koch, a German physician, established four essential conditions under which pathogenic bacteria can infect hosts, and used them to identify the Mycobacterium tuberculosis bacterium that causes tuberculosis. Though both helped establish the germ theory of disease—one of the foundations of modern medicine today—Pasteur and Koch's feud may have been aggravated by nationalism, a language barrier, criticisms of each other's work, and possibly a hint of jealousy.

4. Specialized blood cells are the immune system's greatest weapon.

The most powerful weapons in your immune system's arsenal are white blood cells, divided into two main types: lymphocytes, which create antigens for specific pathogens and kill them or escort them out of the body; and phagocytes, which ingest harmful bacteria. White blood cells not only attack foreign pathogens, but recognize these interlopers the next time they meet them and respond more quickly. Many of these immune cells are produced in your bone marrow but also in the spleen, lymph nodes, and thymus, and are stored in some of these tissues and other areas of the body. In the lymph nodes, which are located throughout your body but most noticeably in your armpits, throat, and groin, lymphatic fluid containing white blood cells flows through vein-like tubules to escort foreign invaders out.

5. The spleen helps your immune system work.

Though you can live without the spleen, an organ that lies between stomach and diaphragm, it's better to hang onto it for your immune function. According to Adriana Medina, a doctor who specializes in hematology and oncology at the Alvin and Lois Lapidus Cancer Institute at Sinai Hospital in Baltimore, your spleen is "one big lymph node" that makes new white blood cells and cleans out old blood cells from the body.

It's also a place where immune cells congregate. "Because the immune cells are spread out through the body," Vance says, "eventually they need to communicate with each other." They do so in both the spleen and lymph nodes.

6. You have immune cells in all of your tissues.

While immune cells may congregate more in lymph nodes than elsewhere, "every tissue in your body has immune cells stationed in it or circulating through it, constantly roving for signs of attack," Vance explains. These cells also circulate through the blood. The reason for their widespread presence is that there are thousands of different pathogens that might infect us, from bacteria to viruses to parasites. "To eliminate each of those different kinds of threats requires specialized detectors," he says.

7. How friendly you're feeling could be linked to your immune system.

From an evolutionary perspective, humans' high sociability may have less to do with our bigger brains, and more to do with our immune system's exposure to a greater number of bacteria and other pathogens.

Researchers at the University of Virginia School of Medicine have theorized that interferon gamma (IG), a substance that helps the immune system fight invaders, was linked to social behavior, which is one of the ways we become exposed to pathogens.

In mice, they found IG acted as a kind of brake to the brain's prefrontal cortex, essentially stopping aberrant hyperactivity that can cause negative changes in social behavior. When they blocked the IG molecule, the mice's prefrontal cortexes became hyperactive, resulting in less sociability. When they restored the function, the mice's brains returned to normal, as did their social behavior.

8. Your immune system might recruit unlikely organs, like the appendix, into service.

The appendix gets a bad rap as a vestigial organ that does nothing but occasionally go septic and create a need for immediate surgery. But the appendix may help keep your gut in good shape. According to Gabrielle Belz, professor of molecular immunology at the Walter and Eliza Hall Institute of Medical Research in Melbourne, Australia, research by Duke University's Randal Bollinger and Bill Parker suggests the appendix houses symbiotic bacteria that are important for overall gut health—especially after infections wipe out the gut's good microbes. Special immune cells known as innate lymphoid cells (ILCs) in the appendix may help to repopulate the gut with healthy bacteria and put the gut back on track to recovery.

9. Gut bacteria has been shown to boost immune systems in mice.

Researchers at the University of Chicago noticed that one group of mice in their lab had a stronger response to a cancer treatment than other mice. They eventually traced the reason to a strain of bacteria—Bifidobacterium—in the mice's guts that boosted the animals' immune system to such a degree they could compare it to anti-cancer drugs called checkpoint inhibitors, which keep the immune system from overreacting.

To test their theory, they transferred fecal matter from the robust mice to the stomachs of less immune-strengthened mice, with positive results: The treated mice mounted stronger immune responses and tumor growth slowed. When they compared the bacterial transfer effects with the effects of a checkpoint inhibitor drug, they found that the bacteria treatment was just as effective. The researchers believe that, with further study, the same effect could be seen in human cancer patients.

10. Scientists are trying to harness the immune system's "Pac-Man" cells to treat cancer.

Aggressive pediatric tumors are difficult to treat due to the toxicity of chemotherapy, but some researchers are hoping to develop effective treatments without the harmful side effects. Stanford researchers designed a study around a recently discovered molecule known as CD47, a protein expressed on the surface of all cells, and how it interacts with macrophages, white blood cells that kill abnormal cells. "Think of the macrophages as the Pac-Man of the immune system," Samuel Cheshier, lead study author and assistant professor of neurosurgery at Stanford Medicine, tells Mental Floss.

CD47 sends the immune system's macrophages a "don't eat me" signal. Cancer cells fool the immune system into not destroying them by secreting high amounts of CD47. When Cheshier and his team blocked the CD47 signals on cancer cells, the macrophages could identify the cancer cells and eat them, without toxic side effects to healthy cells. The treatment successfully shrank all five of the common pediatric tumors, without the nasty side effects of chemotherapy.

11. A new therapy for type 1 diabetes tricks the immune system.

In those with type 1 diabetes, the body attacks its own pancreatic cells, interrupting its normal ability to produce insulin in response to glucose. In a 2016 paper, researchers at MIT, in collaboration with Boston's Children's Hospital, successfully designed a new material that allows them to encapsulate and transplant healthy pancreatic "islet" cells into diabetic mice without triggering an immune response. Made from seaweed, the substance is benign enough that the body doesn't react to it, and porous enough to allow the islet cells to be placed in the abdomen of mice, where they restore the pancreatic function. Senior author Daniel Anderson, an associate professor at MIT, said in a statement that this approach "has the potential to provide [human] diabetics with a new pancreas that is protected from the immune system, which would allow them to control their blood sugar without taking drugs. That's the dream."

12. Immunotherapy is on the cutting edge of immune system research.

Over the last few years, research in the field of immunology has focused on developing cancer treatments using immunotherapy. This method engineers the patient's own normal cells to attack the cancer cells. Vance says the technique could be used for many more conditions. "I feel like that could be just the tip of the iceberg," he says. "If we can understand better what the cancer and immunotherapy is showing, maybe we can go in there and manipulate the immune responses and get good outcomes for other diseases, too."